Smoking Boosts 'Bleeding' Stroke Risk in Those With High Blood Pressure

THURSDAY March 6, 2008 -- Smoking boosts the increased risk of a hemorrhagic stroke already faced by people with high blood pressure, researchers say.

The study examined data on 563,144 people, average age 47, who took part in the Asia Pacific Cohort Studies Collaboration.

More than a third of the participants were smokers at the start of the study. During a median of 6.8 years of follow-up, 746 of the 210,961 smokers and 899 of the 352,183 nonsmokers suffered a hemorrhagic stroke, where a blood vessel bursts inside the brain.

Further analysis revealed that for every 10mm/Hg increase in systolic (when the heart beats) blood pressure, smokers faced an 81 percent increased risk of hemorrhagic stroke, compared with a 66 percent increased risk for nonsmokers.

This added risk of smoking in people with high blood pressure appeared to be specific to hemorrhagic stroke, as there was no evidence to indicate a similar effect on the risk of ischemic stroke (blocked blood flow to the brain) or coronary heart disease, the researchers said.

Smoking may further damage blood vessels in the brain that are already weakened by high blood pressure, the researchers suggested. Weakened blood vessels are prone to rupture and bleeding, thus increasing the risk of hemorrhagic stroke.

Smokers with the highest systolic blood pressure readings (150mm/Hg or greater) were 9.32 times more likely to suffer hemorrhagic stroke than smokers with the lowest readings (120mm/Hg or less). Nonsmokers with the highest systolic blood pressure readings were 7.05 times more likely to suffer hemorrhagic stroke than those with the lowest readings.

The study was published in the current issue of Stroke.

"Smoking and high blood pressure both increase the risk of hemorrhagic stroke. Since we found that these two risk factors have a synergistic effect, quitting smoking and lowering blood pressure will contribute more to preventing stroke than if this previously unreported interaction is ignored," study author Dr. Koshi Nakamura, a visiting research fellow in the nutrition and lifestyle division at The George Institute for International Health in Sydney, Australia, said in a prepared statement.

Study co-author Rachel Huxley noted that hemorrhagic stroke "is an especially debilitating stroke, as about half of the people who have one die as a result of it, while many survivors are left with paralysis or other debilitating effects."

Nakamura said some research suggests that smoking and high blood pressure -- both major risk factors for cardiovascular disease -- are the two most common contributing factors of death in the world, contributing to one in five of all deaths.

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